1. Field of the Invention
The field of invention relates to foamed sulfur asphalts, foamed sulfur asphalt stabilized soils, and methods of formation.
2. Description of the Related Art
During the manufacturing and processing of materials containing asphalt, including asphalt-coated aggregate (asphalt cement), hot asphalt mixes, and foamed asphalt, working temperatures above about 150° C. (about 300° F.) can cause problems for workers and equipment. The sulfur and sulfur compounds present in asphalt, including elemental sulfur and naturally present heterorganic compounds, typically begin to react with other constituents in the asphalt and with the air at temperature above about 150° C. Sulfur forms hydrogen sulfide (H2S) gas, which is toxic to humans, starting at about 151° C. (about 305° F.). Free sulfur in a hydrocarbon environment, including asphalt, dehydrogenates the hydrocarbons present and forms hydrogen sulfide. Heating sulfur to high temperatures in the presence of oxygen forms sulfur dioxide, which is noxious to humans and is an air pollutant.
Sulfur is an abundant and inexpensive material. Elemental sulfur is a byproduct of non-sweet natural gas and petroleum processing. Sources of “free” sulfur include petroleum refineries and gas sweetening plants. Because of the quantity of sulfur extracted from natural gas and petroleum, many sulfur producers consider elemental sulfur a waste product.
It is desirable to find commercial uses for elemental sulfur that can dispose of it in a safe and effective manner. Incorporating sulfur into commercial products can transform what many consider a potential “waste” product into a product with practical value.